This invention relates to a modified, trimerized tolylene diisocyanate and dispersions thereof suitable for use in adhesive and surface-coating compositions.
U.S. Pat. No. 3,860,673 to Lawrence discloses compositions useful in adhesives and surface coatings and comprising (A) an elastomer, for example, a chloroprene polymer; (B) a partly trimerized polyisocyanate, such as tolylene diisocyanate; and (C) a catalyst which is effective to trimerize (B). The partially trimerized isocyanate is used in an amount sufficient to supply 1-10 weight percent of the free -NCO groups based on the elastomer. Adhesive and coating compositions containing the above components normally require a solvent or dispersing medium. Typical adhesive compositions are rubber cements. Usual dispersing media in such applications are aromatic hydrocarbons, aliphatic ketones or esters, or mixtures of two or more such organic liquids, sometimes also containing aliphatic hydrocarbons. Certain solvents used or suitable in the compositions of U.S. Pat. No. 3,860,673 are hazardous to health, especially aromatic hydrocarbons, or are too expensive for industrial applications. Aliphatic hydrocarbons, which are quite inexpensive and whose vapors do not present a serious health hazard, cannot be used in these dispersions by themselves because of virtually complete insolubility of trimerized polyisocyanates therein. Even simple mixtures of aromatic and aliphatic hydrocarbons are unsuitable for this purpose.
It thus is desirable to provide an adhesive or surface-coating composition based on a trimerized polyisocyanate dispersed in a medium comprising principally a mixture of an aromatic hydrocarbon and an aliphatic hydrocarbon.